miR-194调控SUMO蛋白表达:深低温停循环诱导内源性脑保护作用的新机制

Cerebral protection during deep hypothermic circulatory arrest (DHCA) process is mainly dependent on the deep hypothermia, but its protective mechanism is not yet fully elucidated. Traditionally,it is considered to be related to reduce energy metabolism of ischemic neurons. Current study identified that the gene and protein expression play the important role during DHCA. Recent studies confirmed that the brain of hibernating animal can produce endogenous anti-ischemic protein SUMO2 (small ubiquitin-based modified protein).Moreover, the expression of SUMO2 in brain was found increased during hypothermic cardiopulmonary bypass in an animal model.Our previous study found that expression of miR-194 and other 9 miRNAs in the hippocampus of DHCA and normal animals were significantly different, and three targets software predicted SUMO2 is the target of miR-194. We inferred that DHCA stress induced miR-194 down-regulated to active brain endogenous protective mechanism against brain injury by targeting SUMO2. This may be a new mechanism of DHCA in the endogenous brain protection. In order to confirm the new hypothesis from the cellular level identification of the exact target of miR-194;We focus on the protection of miR-194,which can regulate the SUMO2 and downstream related proteins against ischemia insult, by using vivo rats DHCA model and some tools such as luciferase reporter vector and miR-194 lentiviral vector. We will explore the molecular and cellular levels of miR-194 regulation the SUMO2 signal pathway activation mechanism; we use rats DHCA model to assess inhibitors of miR-194 to improve the neuronal function and enhance DHCA cerebral protective effect; this project seeks new perspective to clarify the DHCA as a new target for the production of endogenous brain protection.

深低温停循环（DHCA）过程中的脑保护主要依赖低温，但其机制尚未阐明。传统认为与降低缺血神经元能量代谢有关，目前的观点认为相关基因和蛋白表达的改变至关重要。新近研究证实冬眠动物可产生内源性抗缺血蛋白SUMO2(小泛素化修饰蛋白)，且该蛋白在低温体外循环的脑组织表达增高。我们前期研究发现miR-194等9个miRNAs在DHCA动物海马组织表达差异显著，且三个靶点预测软件均提示SUMO2为miR-194下游靶点。本研究提出"DHCA应激诱导miR-194下调，调控下游SUMO2增高，激活大脑内源性保护机制对抗DHCA后脑损伤"的新假说。拟以大鼠DHCA模型及B35细胞为基础，荧光素酶报告载体及miR-194慢病毒载体为工具，病理结合分子手段，重点探讨miR-194调节SUMO2及下游相关蛋白对抗损伤的内源性脑保护作用。力求从新的视角阐明DHCA诱导的内源性脑保护机制，为脑保护提供全新靶点。

目前大血管和复杂先心病术中，停循环过程的脑保护主要依赖低温，但术后仍存在不容忽视的神经系统并发症。低温停循环期间脑组织损伤及保护机制的阐明，将对临床工作的改善提供方向性指导。本课题建立了新型无血预充大鼠深低温停循环(DHCA)模型，分别在在体和离体条件下，评估了不同温度停循环后的脑组织损伤，并对其损伤与保护的可能分子机制进行了探讨。研究发现：1.不同程度的低温后停循环都出现大鼠脑组织损伤，尤其以神经元的胞质损伤最为明显，主要表现为树突轴突的减少缺失。这些损伤可能是造成术后神经系统并发症的原因。2.低温停循环后大鼠海马区脑组织中小泛素化样修饰蛋白2（SUMO2）的蛋白有降低表现，但与miR-194降低关系不明确。3. 与假手术组相比，浅低温停循环组海马组织中神经元胞质骨架构成蛋白微管相关蛋白2（MAP2）的 mRNA 表达上调。而与假手术组相比，浅低温停循环组的血浆 MAP2 升高。虽然与对照组相比，DHCA组上述改变没有得到统计学差异。但结果提示我们，低温停循环后 , 神经元的树突受损 , 微管溶解,其构成蛋白 MAP2 释放到血液。因此，DHCA后神经系统并发症可能归因于一定程度神经元胞质的损伤，减少损失可能是一种有效的神经保护策略。